People can join this study if they have a confirmed case of locally advanced cutaneous squamous cell carcinoma. They must have at least one tumor on or under the skin that can be measured and injected with the study medicine. They must also have cancer that has gotten worse after taking, or cannot tolerate, a type of treatment called immune checkpoint inhibitors. A team of doctors must agree on this. People can also join if their cancer has spread to nearby areas, such as lymph nodes or skin in between the main tumor area.